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Yajun Wang, Jiaping Wang, Nicolas Holzschuch , Kartic Subr , Jun- Hai Yong, Baining Guo

Real-time Rendering of Heterogeneous Translucent Objects with Arbitrary Shapes. Yajun Wang, Jiaping Wang, Nicolas Holzschuch , Kartic Subr , Jun- Hai Yong, Baining Guo. TexPoint fonts used in EMF.

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Yajun Wang, Jiaping Wang, Nicolas Holzschuch , Kartic Subr , Jun- Hai Yong, Baining Guo

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  1. Real-time Rendering of Heterogeneous Translucent Objects with Arbitrary Shapes Yajun Wang, Jiaping Wang, Nicolas Holzschuch, KarticSubr, Jun-Hai Yong, BainingGuo TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A

  2. Simulating translucency Subsurface scattering

  3. Simulating translucency Subsurface scattering

  4. Previous work

  5. Previous work • Monte-Carlo methods [DEJ99, PH00, LPT05 ]  physically accurate  slow (several hours) [DEJ99] [PH00]

  6. Previous work • Dipole diffusion approximation [JMLH01]  faster (minutes)  homogenous, no complex shape [JMLH01]

  7. Previous work • Extension of Dipole model  real-time [DS03] ,multi-layer[DJ05] , scalable [AWB08]  homogenous [DJ05] [DS03] [AWB08]

  8. Previous work • Precomputed Radiance Transfer[XGL07] [WCPW08]  real-time  precomputation [WCPW08] [XGL07]

  9. Previous work • Diffusion Equation [Ish78, Sta95] Regular grid and multi-grid scheme [Sta95]  first step  off-line The polygrid method [WZT08]  real-time , heterogeneous  simple shape

  10. Challenges 1. real-time rendering and editing 2. heterogeneous materials 3. complex shapes

  11. Our Method 1. in real-time 2. with heterogeneous materials 3. in arbitrary domain

  12. Our Method • Overview • Solving the Diffusion Equation • Quadgraph • Discretized Diffusion Equation • Implementation on GPU • Results • Limitations and Conclusions

  13. Regular grid introduces shape constraints Our domain for diffusion: tetrahedralized geometry Output: Exiting radiance on surface Input: radiance incident on surface Input: radiance incident on surface Diffusion: Flux within object Diffusion Equation +FEM (2D example) Extract exiting radiance from flux at boundary Outgoing radiance Lo Regular Grid Our Method Incoming radiance Li Initialization Iteration Radiant Fluence Optical Properties

  14. Our Method • Overview • Solving the Diffusion Equation • Quadgraph • Discretized Diffusion Equation • Implementation on GPU • Results • Limitations and Conclusions

  15. QuadGraph • Representation of the object volume • GPU-friendly

  16. QuadGraph • Construction : Tetrahedralization Goal: Regular connection Output : 4 classes of tetrahedra [ACSYD05]

  17. QuadGraph • Construction: Splitting Goal: Regular connection Only tetrahedra in C0 and C1 left

  18. QuadGraph • Construction: Transformation Goal: Regular connection C0 inner node inner node + boundary node C1

  19. QuadGraph • Result: Regular connection grid • For inner nodes -> 4 neighbors • For surface nodes -> 1 neighbor

  20. Our Method • Overview • Solving the Diffusion Equation • Quadgraph • Discretized Diffusion Equation • Implementation on GPU • Results • Limitations and Conclusions

  21. Discretized DE • Using the same method in [Sta95] [WZT08] • Based on Quadgraph For inner nodes For surface nodes

  22. Our Method • Overview • Solving the Diffusion Equation • Quadgraph • Discretized Diffusion Equation • Implementation on GPU • Results • Limitations and Conclusions

  23. Preprocess and Storage • Per-node values stored using textures one part for interior nodes one part for surface nodes

  24. Iteration on GPU • Initialization according to the illumination • Iteration on GPU until convergence Initalization During iteration Convergence

  25. Speeding up scheme • GPU cache coherence (Speed + 30%) Packing the data of nodes by its spatial location

  26. Speeding up scheme • Multi-resolution (Speed + >100% ) Several Quadgraphs with different resolution

  27. Our Method • Overview • Solving the Diffusion Equation • Quadgraph • Discretized Diffusion Equation • Implementation on GPU • Results • Limitations and Conclusions

  28. High genus Surface nodes: 121k Inner nodes: 260k Speed: 29.4 FPS

  29. High curvature Surface nodes: 82k Inner nodes: 226k Speed: 22.1FPS

  30. Real-time rendering

  31. Real-time editing of materials

  32. Real-time editing of geometry shape

  33. Speed

  34. Quality

  35. Our Method • Overview • Solving the Diffusion Equation • Quadgraph • Discretized Diffusion Equation • Implementation on GPU • Results • Limitations and Conclusions

  36. Limitations • Materials with high frequency • Deformation changing the topology

  37. Conclusions A new volumetric representation(Quadgraph) for solving the diffusion equation.  Real-time rendering and editing Heterogeneous materials Complex shapes

  38. Questions ?

  39. Thank you!

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